If $a + b = -9$ and $x + y = 5$, what is $-6a - 10y - 10x - 6b$ ?
Solution: $= -6a - 6b - 10x - 10y$ $= (-6) \cdot (a + b) + (-10) \cdot (x + y)$ $= (-6) \cdot (-9) + (-10) \cdot (5)$ $= 54 - 50$ $= 4$